Undercutting drill



Jan- 4, 1950 s. E. CRESSEY UNDERCUTTING DRILL Filed 0st,. 29. 1945 Patented Jan. 24, 1950 UNITED STATES PATENT OFFICE Claims.

This invention relates to an undercutting drill to perform the function of an under-reamer employed for enlarging a well hole below the shoe of a casing. In this type of tool, swinging cutters are pivotally supported in a mandrel and urged outwardly by spring pressure.

One of the objects of the invention is to produce a tool for this purpose, of simple construction, in which the cutters will maintain themselves in a folded condition within the mandrel while it is being passed down the well casing, but which will automatically expand and under-ream the shoe of the casing as soon as the cutters pass below it.

A further object of the invention is to construct the cutters in such a way that the forces and thrusts developed in the cutter tool in operation, will be borne principally by the shank of the tool and the mandrel in such a way as to reliev the pivot pin for the tool of most of these strains.

A further object of the invention is to provide a construction of this type in which the cutters carried by the mandrel will eventually expand to a position in which the thrusts upon the cutters in cutting will themselves maintain the cutters in their expanded condition and without necessitating any further reliance on the springs that constantly urge the cutters toward their expanded relation.

A further object of the invention is to improve the construction for mounting the cutters in the mandrel, and so as to enable them to be quickly mounted and removed when desired, and which will also enable the force of the expanding springs for the cutters to be readily adjusted.

Further objects of the invention will appear hereinafter.

The invention consists in the novel parts and combination of parts to be described hereinafter, all of which contribute to produce an efficient under-cutting drill.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims.

In the drawing:

Fig. 1 is a vertical section taken at the bottom of a well, showing a portion of my improved tool in elevation, the upper and lower portions of the tool being broken away. This view also shows the shoe of the casing in section, and-also a portion of the lower end of the casing broken away, and the cutter tools in a partly expanded position, that is to say, in the relation they will have of the pockets 4.

when they are just emerging from under the lower edge of the shoe.

Fig. 2 is a view similar to Fig. l, but showing half of the under-reamer tool in vertical section, and the other half of the under-reamer tool in side elevation. This view shows the tool located down below the level of the shoe, and with the cutters in a completely expanded relation.

Fig. 3 is a horizontal cross-section taken on the I line 3-3 of Fig. 1 upon an enlarged scale, and shows one of the cutters in section, one of the cutters in plan and with the third cutter absent from the mandrel.

Fig. 4 is a fragmentary view, being a vertical section similar to a portion of Fig. 2, but illustrating a rotary type of cutter instead of a plain type illustrated in Fig. 2. This view shows a portion of the mandrel contiguous to the cutter in section. In this view the cutter is indicated in dotted lines in a folded condition.

Fig. 5 is a face view of the mandrel shown in Fig. 4 as viewed from the left side, and illustrating the cutter in its folded position in the cutter pocket at the side of the mandrel.

Fig. 6 is a plan view of one of the cutters of the type illustrated in Figs. 1 and 2, and illustrating the same in an inclined position and ready to be slipped into its corresponding pocket at the side of the mandrel in Figure 3.

Referring more particularly to the parts, and especially to Figs. 1 and 2, I indicates the lower end of a casing carrying a shoe 2 below which an undercutting or drilling operation is to be performed. This tool includes a mandrel 3 which is provided with a plurality of cutter pockets 4 pref- .erably three in number, and disposed apart as indicated in detail in Fig. 3.

In Figs. 1 to 3 I illustrate the plain type of cutter, that is to say, a non-rotary type, and I provide a cutter 5 of this type corresponding to each Each of these cutters consists of a shank 6 that lies at the extreme inner end of the pocket, and a head I that may project beyond the periphery of the mandrel when a cutting operation is in progress. These cutters 5 are mounted in their corresponding pockets for rotation on a substantially horizontal axis, that enables each cutter to swing outwardly when the mandrel brings the cutters down to about the level illustrated in Fig. 1. They are constantly urged outwardly by a spring or resilient means as will be described hereinafter. As they pass down the casing l, of course the casing holds them back in the pockets, but as soon as they reach the level indicated in Fig. 1, the springs force the cutters outwardly as indicated in Fig. 1. After the under-reaming or drilling operation has progressed further, the cutters will assume a horizontal position as indicated in Fig. 2. In order to accomplish this, means is provided corresponding to each cutter for limiting its outward swingin movement, and in the present instance this means consists in a shoulder or face 3 that forms the upper end wall of the pocket. When the cutters are in a partially expanded condition as indicated in Fig. 1, of course the cutting is largely efifected on their outer edges s and I9, but after the cutters arrive at the position indicated in Fig. 2, most of the cutting will take place on the edge 9. When the cutters are in the position indicated in Fig. 2, very severe stresses are developed in each cutter, and in accordance with my invention I mount the inner end or the shank of each cutter in its pocket in such a way that these stresses developed in the cutter will be imparted directly from the shank of the cutter to the mandrel itself, thereby relieving the pivot pin to be presently described, from any substantial shearing stresses. In order to accomplish this the upper portion to of each pocket is relatively narrow'in width in comparison to the lower portion of the same pocket as shown in Figures 1 and 2 and slightly larger than the thickness of the shank 6, but adjacent the inner end of the shank this pocket portion Ala is bored out laterally to form two laterally spaced arcuate thrust faces II. Furthermore, on each side of each shank I two abutments or tongues I 2 are formed, and the end faces I3 of these tongues or abutments rest As shown tation I4 of the cutter, and in order to enable each cutter to be removed from its pocket, a gap is formed through the forward portions of the arcuate wall II by forming slots I5 cut into the side faces of the narrow portions 4a of the pockets 4. In order to remove each cutter, it is merely necessary to hold it in its folded position, and then pull the same forwardly while the abutments I2 are in alignment with the slots I5. Fig. 5 shows one of the cutters in this folded position, but illustrates a cutter of the rotary type I instead of the plain type indicated in Figs. 1, 2 and 3. At the inner side and toward the central axis of the mandrel, the arcuate faces I I has disposed therebetween a curved contiguous rear thrust face Ila against which abuts the rounded inner end of the shank which is rounded or struck on an are having its center on the axis of rotation Id. In other words the thrust face HA engages the shank directly whereas the spaced arcuate faces II engage the shank abutments I2.

In order to form a positive pivot for each cutter 5 to facilitate its rotation on the axis I I, and also to provide for housing an expansion spring, and at the same time to provide for adjustment of the tension of this spring, I prefer to provide the inner end of the cutter 5 with a cylindrical spring chamber it (see Fig. 3) and at one side of the mandrel I provide a bore 5? for housing the pivot pin, and at the other side and in alignment therewith a larger bore I8 that preferably has substantially the same diameter as the spring chamber or barrel I6. I provide a pivot pin I9 that has a tip at its inner end to be received in the bore I1, and as this end of the pin is of considerably less diameter than the head 2| of the pin, the body of the pin operates as a shank around which a coil spring 22 is disposed. One end of this spring is secured as at 23 in the head of the pin, and the other end of the spring is secured in the inner end of the cutter 5 as indicated at 24. This will enable the spring to exert a force tending to swing the cutter out toward its expanded condition. In order to enable the tension of these springs to be adjusted as desired, the head H is provided with an annular tip or neck 25 at which a socket wrench can be applied to rotate the pin I9 on its own axis. A set screw 26 threaded in the side of the mandrel is provided to engage any one of a plurality of set screw sockets 2'! disposed equidistant on the head 2|. This will evidently enable the tension of each spring to be nicely adjusted. At the same time, the set screw will prevent the pin from working loose.

It will be noted that although it is quite advantageous to house the coil sprin in the inner end of the cutter, one of the results of this is that there is very little bearing area of the pin on the cutter E, and for this reason the presence of the abutments I2 thrusting against the spaced arcuate walls II and the shank 6 thrusting against the contiguous Wall I Ia is most advantageous.

Instead of providing plain cutters such as the cutters 5, I may construct the cutters as indicated in Figs. 4 and 5, so that each cutter presents a body 28 of shank form, the outer end of which rotatably carries a rotary cutter 2S3 mounted to rotate on the longitudinal axis of the body 28. This type of cutter, however, is mounts-cl in the mandrel in the same Way as illustrated in Figs. 1, 2 and 3. It is, however, necessary to provide a laterally enlarged pocket 30 to house the rotary cutter 29 as indicated in the dotted lines in Fig. 4 and the full lines in Fig. 5. In other respects the construction for mounting the shank body 28 and for enabling the same to be removed from the mandrel, is substantially the same as in the embodiment of the invention illustrated in Figs. 1, 2, and 3. The upper end of the mandrel 3 may be provided with a tapered pin 35, enabling it to be attached to the lower end 32 of a drill string. The mandrel is, of course, provided with a mud circulation opening or passage 33.

Many other embodiments of the invention may be resorted to Without departing from the spirit of the invention.

What I claim is:

1. In an undercutting drill, the combination of a mandrel adapted to be passed down a well casing and past the shoe, said mandrel having cutter pockets in the side thereof, a cutter mounted in each pocket for rotation on an axis to swing out substantiall radially from the mandrel, said pockets having slots in their side walls and each cutter having a shank fitting into the pocket, and having abutments on its sides capable of passing through the slots when the cutter is being placed in, or removed from, its pocket, each pocket having a laterally formed socket with an arcuate wall back of its slot to permit the rotation of the cutter on the said axis after the cutter has been passed inwardly into its pocket, and said arcuate wall cooperating with the abutments to take the thrust of the cutter, a plurality of springs, one spring of each corresponding to each cutter and urging the same outwardly, and means for limiting the outward swinging movement of the cuttters after they have passed below the shoe.

2. In an undercutting drill, the combination of a mandrel adapted to be passed down a well casing and past the shoe, said mandrel having cutter pockets in the side thereof, a cutter carried in each pocket and adapted to be passed into the pocket by a radial movement toward the axis of the mandrel, the wall of said mandrel adjacent each pocket having a first bore at one side, and a second bore at the opposite side of relatively larger diameter, a pivot pin having a tip mounted in the first bore of smaller diameter and having a relatively larger head received in the second bore of larger diameter, the inner end of said cutter having a, spring chamber therein, a coil spring received in said spring chamber with one and secured to the pin and the other end exerting force against the cutter in a direction to swing the same out of the pocket, said pin head having means for adjustably rotating the same and having set screw sockets on its side face; and a, set screw mounted in said mandrel and adapted to engage any one of said set screw sockets to hold the pin against rotation.

3. In an undercutting drill, the combination of a mandrel adapted to be passed down a Well casing and past the casing shoe, said mandrel having a cutter pocket in the side thereof, a cutter having a shank extending radially into the upper end of said pocket and having a head projecting outwardly from the side of the mandrel, th upper end of said pocket having arcuate walls in the side faces thereof, and the side faces of said shank having abutments, the outer faces whereof bear against the said arcuate walls to assist in taking the thrust of the cutter while in operation, and to assist in centering the cutter for rotation on an axis within the pocket, and a pin mounted in the wall of the mandrel and passin through the shank of the cutter, a spring at least partially housed in said cutter for urging said cutter to swing outward, the lower portion of said pocket being capable of receiving and housing the head of the cutter when the cutter is in a folded condition while the mandrel is being passed down the casing, the said arcuate walls having gaps cut therethrough in the form of slots in the side faces of the said pocket, enabling the abutments on the shank to pass outwardly when the cutter is being removed from the pocket.

4. In an undercutting drill, the combination of a mandrel adapted to be passed down a well casing and past the casing shoe, said mandrel having a cutter pocket in the side thereof, a cutter having a shank extending radially into the upper end of said pocket and having a head projecting outwardly from the side of the mandrel, the upper end of said pocket having arcuate 6 thrust walls in the side faces thereof, and the side faces of said shank having abutments, the outer faces whereof bear against the said arcuate walls to assist in taking the thrust of the cutter while in operation, and to assist in centering the cutter for rotation on an axis within the: pocket, a pin mounted in the wall of the mandrel and passing through the shank of the cutter, a spring at least partially housed in said cutter for urging each cutter to swing outward, the lower portion of said pocket being capable of receiving and housing the head of the cutter when the cutter is in a folded condition while the mandrel is being passed down the casing, thesaid arcuate walls having gaps cut therethrough in the form of slots in the side faces of the said pocket, enabling the abutments on the shank to pass outwardly when the cutter is 7 being removed from the pocket.

5, In an undercutting drill, the combination of a mandrel adapted to be passed down a well casing and past the casing shoe, said mandrel having a cutter pocket in the side thereof, a cutter having a shank extending radially into the upper end of said pocket and having a head projecting outwardly from the side of the mandrel, the upper end of said pocket having arcuate sockets in the side faces thereof, and the side faces of said shank having abutments, the outer faces whereof bear against the said arcuate walls to assist in taking the thrust of the cutter while in operation, the lower portion of said pocket being capable of receiving and housing the head of the cutter when the same is in a folded condition while the mandrel is being passed down the casing, the said arcuate wall having gaps cut therethrough in the form of slots passing outwardly on the side faces of the said pockets to enable the abutments on the shank to pass outwardly when the cutter is being removed from the pocket, the inner end of said shank having a spring chamber formed therein, and a coil spring mounted in the spring chamber and urging the cutter to swing outwardly beyond the periphery of the mandrel.

STEVE E. CRESSEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 631,423 Fauck Aug. 22, 1899 997,718 Swan July 11, 1911 1,131,928 Griflin L'Mar. 16, 1915 1,179,284 Cox Apr. 11, 1916 1,427,064 Caverly Aug. 22, 1922 1,510,222 Herman Sept. 30, 1924 1,899,727 Sandstone Feb. 28, 1933 

